1. Field of the Disclosure
The present disclosure relates to a magnetic contactor that uses a coil having a broad rated voltage range and is compactly configured.
2. Background of the Disclosure
Generally, magnetic contactors are devices that switch power (a current) flowing in a main circuit by using the electromagnet principle. The magnetic contactors may be divided into, for example, medium•low-capacity products of less than 130 A and high-capacity products of 130 A to 800 A depending on a current capacity.
FIG. 1 is an exploded perspective view schematically illustrating a configuration of a general medium•low-capacity magnetic contactor. The magnetic contactor includes a first frame 11, a movable core 12, a backspring 13, a bobbin 14, a fixed core 15, and a second frame 16.
The bobbin 14 is a cylinder-shaped hollow iron core. When external power is applied to a coil 14a which is wound around an outer surface of the bobbin 14, a magnetic field is generated around the coil 14a, and the fixed core 15 having an E-shape is magnetized by the magnetic field to become an electromagnet.
The fixed core 15 changed to the electromagnet absorbs and downward attracts the movable core 12 of a conductor with a magnetic force, and a movable contact mechanically connected to the movable core 12 is lowered to contact a fixed contact. Therefore, a current flows in a main circuit.
At this time, when the power applied to the coil 14a dissipates, the magnetic field generated around the coil 14a is also released, and thus, the movable core 12 disposed on the backspring 13 is raised to the original position by an elastic restoring force of the backspring 13. Therefore, the movable contact is separated from the fixed contact, and thus, the current flowing in the main circuit is cut off.
In a prior art magnetic contactor, a rated voltage of a coil for operating a main contact (a movable contact and a fixed contact) is differently applied to products. For example, the rated voltage of the coil applied to the prior art magnetic is set to 24 V, 48 V, 100 V, 220 V, 240 V, 380 V, 440 V, 480 V, and 600 V. In each magnetic contactor, the rated voltage of the coil is marked on a manipulation coil terminal. That is, a coil applicable to each magnetic contactor is determined depending on the rated voltage of the coil.
According to the safety standard of the prior art magnetic contactor, in a first condition, in order to secure a reliability of a switch operation, although an external source voltage is within 85% to 110% of a rated voltage of a coil, when the rated voltage of the coil is, for example, 100 V, a fixed contact should operate as a movable contact even though only an external voltage of 85 V is applied to the coil. This is because a voltage of a power system is changed depending on a zone and a place in which a magnetic contactor is used.
In a second condition, even though an external source current applied to a coil is continued for a certain time (for example, two hours) or more, a temperature of the coil should not exceed a limited temperature (for example, 65 degrees C.).
The reason will now be described with reference to FIG. 2. FIG. 2 is a circuit diagram of a manipulation circuit part of a low-capacity magnetic contactor of the prior art. In the manipulation circuit part, since an external source voltage is applied to both ends of a coil L as-is, when an external source current is continuously applied to the coil L, a temperature of the coil L exceeds the limited temperature (for example, 65 degrees C.), and a resistance of the coil L increases. For this reason, a movable contact cannot operate.
In the prior art low-capacity magnetic contactor, when a voltage equal to 85% of a rated voltage of the coil L is applied to the coil L, the movable contact operates at an initial stage. However, since the external source current applied to the coil L is continued for a certain time or more, the coil L is deteriorated, and the resistance of the coil L increases. For this reason, it is unable to maintain a connection state of a contact.
Therefore, all the first and second conditions based on the safety standard should be satisfied.
Moreover, in the prior art magnetic contactor, the movable core 12 and the fixed core 15 have an E-shape, and thus, a space occupied in a frame is large. For this reason, there is limitations in simplifying a structure of a product and miniaturizing the product.